We are conducting this study to determine whether other drugs used to treat opiate dependence have significant effects on AZT disposition. To date 27 subjects have completed the study and the enrollment goal for the entire study is 80. The proposed studies represent a method for identification of potential drug interactions in the AIDS population, which is cost-effective. These investigations will make a significant contribution to improved medical and substance abuse treatment in opioid-dependent patients with HIV disease. The study will continue for an additional 2 years.